Syntax Question

[aruawons]

#define foo(buf, data) *(buf)++ = (char)(data)
Can someone help to explain the above syntax of the token string:
*(buf)++ = (char)(data)
?
It works but I just don't understand what it does.
Thanks!

[Caligulaminus]

The cast to char value of data is copied to the position buf points to, afterwards buf is incremented by 1.